for all you engineers out there . when a product calls for 9v 300 ma that's what you get with the unit.

Question

i know if you have too much or too little you might cause damage by component failure such as a burn out from too much voltage . im certain too little with cause the unit to fail to opperate and too much might might burn it up?. same with amperage . if not enought you may not get unit to work . but if its more shouldnt it work . you have 15 amp current in your home power but you use only the part of it that the product needs to function. what is right .? can i use a power supply that is stronger than stated in the requirements ?. more volts and/or more amps ? . please help im creating a pc network of old pcs and spare equipment for a church youth group and need to use anythig i can to make it work.

Answer 1

Many people ask similar questions. -- you are not alone, and
the " answer " is more difficult than a cut-and-dried answer.

First
The "rating " listed as "needed " is an approximation.

Second
The rating listed on adapters is an approximation

Third
When a load is placed on many common adapters, the
voltage DROPS proportional to the load

Fourth
(newer SWITCHMODE regulated, computer grade power adapters actually regulate the voltage, and " should "
generate the exact voltage, within the stated limits on the
label)

Here is a previous answer that covers a great deal of
general information that you should review :

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iscwest
5 months ago



What happens when a camcorder requires 7.9volts and you plug in a 7.5 volt adapter?

Its a Panasonic PV-GS31 camcorder.


robin_graves
5 months ago



Best Answer - Chosen by Asker

You need to know what AMPERAGE - milliamps the Camcorder is rated for at the 7.9 listed voltage. Adapters almost NEVER give the voltage that the label indicates - if you have a digital multimeter and look at the voltage, you will usually find that 7.9 volts actually reads 14 or 16 volts with no "load" ( not plugged in ) as the camcorder uses power the
voltage will drop, and the Amperage will increase - different
functions on the camcorder such as rewind, zoom, playback etc. will use different motors and chips, and therefore use different amounts of power. Some adapters use cheap
single diode converters from AC ( Alternating current input of 120 volts, which goes from zero to 167 vots in one direction, back to zero, then to 167 volts in the other direction, and back to Zero ) If there is little or no CAPACITOR value in MicroFarads, then the output is a choppy
jagged pulse. The Output rating of 7.9 volts at xxx milliamps ( one thousand milliamps is one amp ) is an AVERAGE only - at one specific amperage listed !
NOTE - you also need to know the center tip and outer
adapter plug poarity ( Positive and negative ) of the
replacement 7.5 volt adapter ! ! ! make certain that the
positive and negative match the required 7.9 volt inputs.
If you use a 3 AMP ( 3000 milliamp ) 7.5 volt adapter,
it may work much better than a 1100 milliamp 7.9 volt
adapter, since when the Camcorder uses a lot of power, the
7.9 volt may drop to 7.3 volts under heavy load, but the
7.5 volt ( "RATED" ) adapter may actually put out
9 raw volts, and NEVER drop below 7.5 volts with the
3000 milliamp ( "power output " ) it is capable of supplying. Unless I find a computer grade switch mode power supply rated a 5.0 volts, xxx amps, I rarely find any
adapter that actually puts out the VOLTAGE that is listed
on the label. Ten different adapters, by ten different
companies, all with the same output label ( 7.5 volts at
1000 milliamps ), will actually give 10 different voltages
at any given load ( Current draw in milliamps ).
Just make certain that the polarity ( Positive and negative ) is correct, and try the 7.5 - if the adapter gets too hot in a few minutes of use, then it is too small in its Amperage output, and you could burn it out. If it has an equal, or higher amperage than the original 7.9 adapter, and it remains cool running, and the camcorder works perfectly, then you are probably ok.
Summary - check the polarity and the amperage required. If your 7.5 volt adapter is labelled 200 or 450 milliamps then you are probably in trouble - the adapter is for a tiny device that uses little power. If the camcorder label states
1.6 amps ( at 7.9, or " 8 " volts ) then you are better off to try to find an adapter with similar or HIGHER amperage output, at, or near 7.5 to 8 volts, for example 2 amps ( 2000 milliamps ). If you had 2 electrical meters, one set to amperage, the other set to votlage, you could see the actual voltage of any adapter drop from, for example, 12 vots raw output, with no load, to 7.9 volts under heavy camcorder load when plugged in.
NOTE 120 Vots is not 120 volts of anything - it is an AVERAGE of the curve going up and down from zero to about 167 vots at the peak of each "hill" in the center. The wave form of 120 volts looks like a bunch of hills, alternating
with identical valleys, so the average "real" power is
about 120. If you look at an oscilloscope you see a sine wave, which looks like the side view of ripples in water.
If you had to say how high the water level was, and there were waves comming in on the beach, you take the average between the tops of the waves and the bottoms, and use that as an average. Similar to "120" volts, or 7.9 volts Direct current ( Direct Current is exactly the same a a battery output - just a single voltage with no waves - just a straight line, like a water level on a day with no wind - flat ) Most adapters put out some form of ripple or waves caused by the 120 volt input's huge waves.
So, 7.5 and 7.9 "could" be almost identical, depending on
how well the adapters were made, and what electronics were used inside the adapters to change 120 volts down to " 7.9 ".
FINALLY, if I haven't bored you to death already, the CAMCORDER itself usually has a power regulation circuit
built into it as well ... This means that the Camcorder takes in the raw "7.9 volts" and has circuits to change the power to charge the camcorder's batteries ( high current, probably about 6 volts ), to run the motors ( probably
various tiny motors running 6 volts, 5 volts, 3 volts etc
depending on how powerful they need to be ), to run the memory and controller chips, (5.00 volts, 3.3 volts, 1.5 volts, etc. ) and to supply the mini liquid TV viewer screen's backlight... SO... This means that even a 9 volt
power supply with a correct polarity, and similar Amperage rating may work just fine, IFF the power converter circuits in the Camcorder itself can handle dropping a bit of excess voltage from the 9.0 volts ( rated, but putting out 12 volts raw power easily under no load ) to 8.0 ( or 7.9 ) volts rated by the Camcorder manufacturer. Again Amperage rating is a huge factor to consider...


_______________________________________________

As you can see from my previous typical answer, the stated
desired voltage and amperage may not be exactly correct,
and the adpaters themselves may not exactly deliver the
voltages and amperages stated on the labels.

If you are plugging in typical home amplified speakers, you will
find that the voltages and amperages can vary a GREAT deal,
and still work ok. If the speakers state 6 Volts, you can probably
use 5 Volts, 6 volts, 7.5 volts, and 9 volts with almost no
change in sound, as long as the AMPERAGE of the adapters
is "close" to the stated rating. As the VOLTAGE goes UP, in
this example, the amperages of the adapters can be LESS, since
as the adapter might be 9 volts at 400 MilliAmperes ( 400 mA )
and the speakers state 600 mA at 6 Volts, remember that
the 9 Volt adapter ( if it is not a switch mode computer grade
adapter ), really puts out a pulse of DC, " averaged " at 9 volts,
" WITH " a load of 400 milliamps. Raw output, un-averaged might well be 12.4 volts, with no load. Since you would be using the adapter on a " 6 Volt " device, the drop in demand from 9 volts to 6 volts, will INCREASE the available AMPS that the adapter can
easily deliver, since the adapter is running at a fraction of its
limits...
Having a simple Digital multimeter handy really will be helpful in
your tasks in the future, and I recommend you get one. If the
meter has an AMPERAGE range on it, you can plug the meter
in Series ( the power from the adapter goes THROUGH the
meter ) and you can visually see the current being used by the
speakers ( or whatever device ). If you start the speakers with
volume on low, and slowly turn them up, you will see the current
( Amperage ) go up, and if the current Chops, or drops, you know
the adapter can't handle the load.
Checking for how HOT the adapter gets under 10 minutes of load is another easy test, and of course, in the example of the speakers, if you turn up the speakers full volume and the sound
starts to rattle or chop, you are under powered...

hope this helps give you an idea of what to look for, and
where to begin...

In you specific example, I would try a 7.5, a 9, a 10, and even
a lower amperage 12 volt ( non switchmode ) adapters, and
check the voltages before and after being connected. the 12 volt
adapter can typically give 16 volts of raw, no-current voltage, so
it is the most risky. None of the 7.5, 9, or 10 volt adapters will
show 7.5, 9 or 10 volts when not plugged in to the speakers..
A higher amperage 6 volt adapter may show 9 volts raw,
and even power a " 9 Volt " device with no problems, and, again
only trial and error would tell, since there are thousands of
adapter designs, and thousands of speaker designs, each delivering different characteristics.
Amperage, on an adapter is probably more critical on 6, 7.5, and
9 volts devices. the most common mistake is to use a
BATTERY CHARGER adapter on something like speakers,
and shorting out the teeny 40 to 120 milliAmp adapter.
The second biggest mistake is for someone to grab an adapter that appears to have the correct rating - 9 Volts, 300 mA,
and plug it in --- but forgetting to read the OUTPUT as AC or
Alternating current, and blowing up the device.
The third mistake is to get the Volts, and Amps correct, say
9 Volts, 500 m A ( more than enough ), and have the adapter
plug with positive and negative terminals REVERSED, and
thus blow up the device...

Take your time, read the labels carefully, and if at all possible,
check the adapter output with a multimeter !

The other possibility, since 300 milli amps is rather small for
a " COMPUTER " device, is that the adapter you want is a
CHARGER for a device such as a rechargeable mouse, or
a rechargeable keyboard, or whatever. Manufacturers, unfortunately, for rechargeable adapters, have been traditionally very cheap, and if you are trying to find an adapter for this
purpose, please be even MORE cautious. I have over 30 cell phones, and the rated voltage and amperage on all adapters
has almost nothing to do with the actual readings. Two different
adapters ( from the same manufacturer ) with the same ratings
will put out out radically different voltages, and with lithium ion
batteries, the situation is explosively critical... !
For " dumb " devices like speakers, you have much more room
to experiment...

good luck

Answer 2

If you're hooking up a lot of older hardware you may want to invest in some surge protection. Some of the older stuff is pretty touchy and a surge could be devastating.
Just be sure when you hook up your transformers(power supplies) they match whats on the unit for the volts. The amps/milliamps will take care of themselves.

Answer 3

The voltage rating of a power supply is it's voltage.
The amps rating is the maximum amps it is rated to supply. Any power supply that has an amp rating that meets or exceeds the draw of the load will work.